Data transmission method and related device

Abstract

The method includes: handing over a first terminal device from a second terminal device to a network device; receiving, by the first terminal device, a first packet data convergence protocol PDCP data packet sent by the network device; and if the first PDCP data packet is a target PDCP data packet, submitting, by the first terminal device, a second PDCP data packet, where the target PDCP data packet is a PDCP data packet sent by the network device based on a transmission status report, and the transmission status report is a status report sent by the first terminal device or the second terminal device to the network device.

The invention claimed is: 
     
       1. A data transmission method, comprising:
 handing over a first terminal device from a second terminal device to a network device; 
 receiving, by the first terminal device, a first packet data convergence protocol (PDCP) data packet sent by the network device; and 
 submitting, by the first terminal device, a second PDCP data packet, wherein a target PDCP data packet is a PDCP data packet sent by the network device based on a transmission status report. 
 
     
     
       2. The data transmission method according to  claim 1 , wherein, after the handing over the first terminal device from the second terminal device to the network device, the method further comprises:
 sending, by the first terminal device, the transmission status report to the network device. 
 
     
     
       3. The data transmission method according to  claim 1 , wherein after the first PDCP data packet is a next PDCP data packet of a last submitted PDCP data packet, the first PDCP data packet is the target PDCP data packet, and the last submitted PDCP data packet is a PDCP data packet that is submitted latest among the PDCP data packets submitted by the first terminal device. 
     
     
       4. The data transmission method according to  claim 3 , wherein the method further comprises:
 after the first PDCP data packet is the target PDCP data packet, 
 setting, by the first terminal device, a PDCP reordering indication as a first indication. 
 
     
     
       5. The data transmission method according to  claim 3 , wherein the method further comprises:
 after the first PDCP data packet is the target PDCP data packet, and a sequence number of the first PDCP data packet is equal to a sequence number of a first missing PDCP data packet indicated in the transmission status report, 
 setting, by the first terminal device, a PDCP reordering indication as a first indication. 
 
     
     
       6. The data transmission method according to  claim 3 , wherein the method further comprises:
 when the first sequence value is less than a sequence value of the first missing PDCP data packet, after the first PDCP data packet is the target PDCP data packet, a sequence value of the last submitted PDCP data packet is greater than or equal to the first sequence value, and the sequence value of the last submitted PDCP data packet is less than the sequence value of the first missing PDCP data packet, 
 setting, by the first terminal device, the PDCP reordering indication as the first indication, wherein the first sequence value is a sequence value corresponding to the PDCP data packet indicated in the transmission status report. 
 
     
     
       7. The data transmission method according to  claim 4 , wherein the method further comprises:
 after the PDCP reordering indication is the first indication, submitting, by the first terminal device, wherein the PDCP data packet of which the count value is less than the count value of the first PDCP data packet; and 
 submitting, by the first terminal device, the second PDCP data packet. 
 
     
     
       8. A plurality of terminal devices, each of the plurality of terminal devices comprising:
 a processor; 
 a memory; and 
 a transceiver, wherein the memory is configured to store program code, the plurality of terminal devices include a first terminal device and a second terminal device, and the processor of the first terminal device is configured to execute the program code to 
 perform a process of handover from a second terminal device to a network device; 
 receive, by using the transceiver, a first PDCP data packet sent by the network device; and 
 submit a second PDCP data packet, wherein a target PDCP data packet is a PDCP data packet sent by the network device based on a transmission status report. 
 
     
     
       9. The plurality of terminal devices according to  claim 8 , wherein the processor of the first terminal device is further configured to
 send, by using the transceiver of the first terminal device, the transmission status report to the network device. 
 
     
     
       10. The plurality of terminal devices according to  claim 8 , wherein after the first PDCP data packet is a next PDCP data packet of a last submitted PDCP data packet, the first PDCP data packet is the target PDCP data packet, and the last submitted PDCP data packet is a PDCP data packet that is submitted latest among the PDCP data packets submitted by the first terminal device. 
     
     
       11. The plurality of terminal devices according to  claim 10 , wherein the processor of the first terminal device is further configured to perform:
 after the first PDCP data packet is the target PDCP data packet, setting a PDCP reordering indication as a first indication. 
 
     
     
       12. The plurality of terminal devices according to  claim 10 , wherein the processor of the first terminal device is further configured to, after the first PDCP data packet is the target PDCP data packet, and a sequence number of the first PDCP data packet is equal to a sequence number of a first missing PDCP data packet indicated in the transmission status report,
 set a PDCP reordering indication as a first indication. 
 
     
     
       13. The plurality of terminal devices according to  claim 10 , wherein the processor of the first terminal device is further configured to, when a first sequence value is less than a sequence value of the first missing PDCP data packet, after the first PDCP data packet is the target PDCP data packet, a sequence value of the last submitted PDCP data packet is greater than or equal to the first sequence value, and the sequence value of the last submitted PDCP data packet is less than the sequence value of the first missing PDCP data packet,
 set the PDCP reordering indication as the first indication, wherein the first sequence value is a sequence value corresponding to the PDCP data packet indicated in the transmission status report. 
 
     
     
       14. The plurality of terminal devices according to  claim 11 , wherein the processor of the first terminal device is further configured to, after the PDCP reordering indication is the first indication,
 submit the PDCP data packet of which a count value is less than a count value of the first PDCP data packet, and 
 submit the second PDCP data packet. 
 
     
     
       15. The plurality of terminal devices according to  claim 9 , wherein after the first PDCP data packet is a first missing PDCP data packet indicated in the transmission status report, the first PDCP data packet is the target PDCP data packet, and the processor of the first terminal device is further configured to
 submit the PDCP data packet of which a count value is less than a count value of the first PDCP data packet. 
 
     
     
       16. The plurality of terminal devices according to  claim 15 , wherein the processor of the first terminal device is further configured to
 release the transmission status report. 
 
     
     
       17. A network device, comprising:
 a processor; 
 a memory; and a 
 transceiver, wherein the processor, the memory, and the transceiver are connected to each other, the memory is configured to store program code, and the processor is configured to execute the program code to 
 receive, by using the transceiver, a transmission status report sent by a first terminal device or a second terminal device, wherein the transmission status report is used to feed back a receiving status of data that is sent by the network device to the first terminal device by using the second terminal device before the first terminal device is handed over to the network device, and 
 after the first terminal device is handed over from the second terminal device to the network device, send, by using the transceiver, a target PDCP data packet to the first terminal device based on the transmission status report.